(CN) – British Prime Minister Boris Johnson faces the first major setback of his new role as his promise to ensure a Halloween withdrawal from the European Union, with or without a deal, goes before the House of Commons for a vote Tuesday.

In the event that Johnson’s government loses that vote, he might seek to call snap elections for Oct. 14 before the U.K. is due to leave the EU.

Johnson’s day did not start out well. In the House of Commons, as he was updating Parliament about the recent G7 summit, a Tory member dramatically entered the chamber and then sat down among the members of the Liberal Democrats.

With the defection of former Tory Phillip Lee to the Liberal Democrats, Johnson’s government effectively lost its majority in Parliament. Lee was among a group of rebel Conservatives who are ready to vote against Johnson and join opposition parties on Tuesday evening.

“I haven’t left my party, my party has left me. My values have remained the same,” Lee said afterward in explaining his decision to switch parties to Sky News television. The Liberal Democrats favor the U.K. remaining in the EU.

That proved to be just the start of a fiery session of Parliament, with Johnson at times fiercely attacking his opponents, in particular the leader of the Labour Party, Jeremy Corbyn.

“There is only one way to describe this bill,” Johnson said of the proposed bill to stop his government from pursuing a no-deal Brexit. “It is Jeremy Corbyn’s surrender bill.”

Corbyn shot back that Europe is not the enemy. “We’re not surrendering because we are at war with Europe. They are surely our partners.”

Efforts to stop Britain from exiting the EU without a deal are playing out in court as well after Johnson got the queen to suspend Parliament for nearly five weeks between September and Oct. 14. In Edinburgh, lawyers for 75 parliamentarians opposed to Brexit asked a judge Tuesday to halt the suspension.

Johnson’s opponents say his sidelining of Parliament was a cynical maneuver to ease the country’s exit from the EU without a deal and to curtail debate. As it stands now, the U.K. will leave the EU on Oct. 31 unless that deadline is pushed back.

Johnson took over the prime minister’s office at No. 10 Downing Street in late July on a pledge to ensure the U.K. leaves the EU “do or die” on Oct. 31. He has continued to make that pledge and stepped up preparations for a no-deal exit.

He and other pro-Brexit members of the Tory party argue that Britain must leave the EU, even if that means doing so without first spelling out the terms of the divorce in a deal. Johnson took over the premiership after Parliament rejected a wide-ranging deal hammered out by his predecessor, Theresa May — one thatmaintained close ties with the EU.

Though May’s deal fractured Parliament, economists warn that leaving without a deal could lead to economic disaster. Under such a scenario, there are concerns that there could be food and medicine shortages, widespread disruption to commerce, frayed political relationships with Europe, and the possibility of a return to border checks between Ireland and Northern Ireland, which in turn could threaten peace in the volatile region.

The House of Commons returned to work on Tuesday after a summer recess. It is expected to vote this evening on a bill that proposes to force Johnson to ask for Brexit to be delayed until Jan. 31 unless Parliament has approved a new deal or voted in favor of leaving the EU without a deal.

Johnson’s government has said it will call for new elections if Parliament votes to take control of the Brexit exit date. Johnson said Monday in a televised speech that he did not want an election but warned Parliament not to vote against his efforts to leave the EU on Oct. 31. He said a vote against him would “plainly chop the legs out from under the U.K. position” in negotiations with the EU over a new deal. He said it would “make any further negotiation absolutely impossible.”

Johnson says his government is in talks with the EU about renegotiating May’s deal, in particular a crucial section dealing with the question of Northern Ireland.

May and the EU agreed that Northern Ireland would remain closely aligned with the EU’s rules, laws and customs in the event that a future trade agreement cannot be worked out between the U.K. and the EU.

Keeping Northern Ireland aligned to the EU is seen as critical to ensure that a border is not erected between Northern Ireland and Ireland, thus allowing the free flow of commerce and people to continue without disruption.

The EU has said it will not change its position on the Northern Irish border. British media reported that negotiations between Johnson and the EU over the border were not progressing well.

Johnson and others who want Britain to make a clean break with the EU warn that keeping Northern Ireland aligned to the EU would in turn leave the rest of the U.K. also closely tied to the EU. They argue that such an arrangement betrays the will of the 52% of voters who backed leaving the EU in the 2016 Brexit referendum.

Opponents, though, say the dilemma and impasse over Brexit is so bad that the U.K. should hold a second referendum to determine the country’s future. They argue that voters cast ballots in the referendum not fully aware of what leaving the EU would mean and that now, after three years of debate, voters are better informed.

(Courthouse News reporter Cain Burdeau is based in the European Union.)